在下面的代码中，在文本字段的整数和双倍值之间做计算数时，如何应用双向方法？

Question

    StringConverter<Number> converter = new NumberStringConverter();
    StringConverter<Double> toDouble = new DoubleStringConverter();
    
    TextFormatter<Number> quantity = new TextFormatter<>(converter);
    TextFormatter<Double> price = new TextFormatter<>(toDouble);
    TextFormatter<Double> total = new TextFormatter<>(toDouble);

    Quantity.setTextFormatter(quantity);
    Price.setTextFormatter(price);
    Total.setTextFormatter(total);
    
    total.valueProperty().bindBidirectional(Bindings.createObjectBinding(() -> {
        
        // ?????????????????????????????????????????
        
    }, quantity.valueProperty(), price.valueProperty()));
    

请帮助填写计算或任何其他方法来触发更改，每当我输入不同的数字的文本字段？

Answer 1

由于表示总计的文本字段不可编辑，因此这里不需要双向绑定，只需要在计算值更改时更新一个值（总计的值）的常规绑定。

你可以做一些类似的事情

total.valueProperty().bind(Bindings.createObjectBinding(
    () -> quantity.getValue() * price.getValue(),
    quantity.valueProperty(), price.valueProperty()));

bindings.createxxxbinding(...)方法创建可观察的值，这些值是计算出来的（这里基本上是通过公式quantity*price)。绑定表达了这样一个事实，即当计算值更改时，total的值应该更改。双向绑定表达了这样一种思想，即当两个值中的任一个发生变化时，应将另一个设置为与之匹配。这在这种情况下根本行不通，因为您无法设置计算值。

import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.geometry.HPos;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.control.TextFormatter;
import javafx.scene.layout.ColumnConstraints;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;
import javafx.util.converter.DoubleStringConverter;
import javafx.util.converter.IntegerStringConverter;


public class App extends Application {

    @Override
    public void start(Stage stage) {
        
        TextFormatter<Integer> quantity = new TextFormatter<>(new IntegerStringConverter(), 0);
        TextFormatter<Double> price = new TextFormatter<>(new DoubleStringConverter(), 0.0);
        TextFormatter<Double> total = new TextFormatter<>(new DoubleStringConverter(), 0.0);
        
        
        
        total.valueProperty().bind(Bindings.createObjectBinding(
                () -> quantity.getValue() * price.getValue(), 
                quantity.valueProperty(), price.valueProperty()));
        
        TextField quantityTF = new TextField("0");
        quantityTF.setTextFormatter(quantity);
        
        TextField priceTF = new TextField("0.0");
        priceTF.setTextFormatter(price);
        TextField totalTF = new TextField();
        totalTF.setEditable(false);
        totalTF.setTextFormatter(total);
        
        
        GridPane root = new GridPane();
        ColumnConstraints leftCol = new ColumnConstraints();
        leftCol.setHalignment(HPos.RIGHT);
        ColumnConstraints rightCol = new ColumnConstraints();
        rightCol.setHalignment(HPos.LEFT);
        root.getColumnConstraints().setAll(
                leftCol, rightCol
        );
        root.setAlignment(Pos.CENTER);
        root.setPadding(new Insets(5));
        root.setHgap(5);
        root.setVgap(5);
        root.addRow(0, new Label("Price:"), priceTF);
        root.addRow(1, new Label("Quantity:"), quantityTF);
        root.addRow(2, new Label("Total:"), totalTF);
        
        stage.setScene(new Scene(root, 800, 500));
        stage.show();
    }

    public static void main(String[] args) {
        launch();
    }

}